SB 


JC-NRLF 


SB    bfl 


THE  HARROW-LEAVED   MLK7/SHD 

and 

THE  BROAD-LEAVED   OH  'SHOWY  MILKWEED 
PLAITTS    POISONOUS   TO  LIVESTOCK  III   AMERICA 

By  C.  E.  Fleming  and  N.  P*  Peterson 
Univ.  of  Nevada  Bui.  -//99.    December  1920. 


THE  UNIVERSITY  OF  NEVADA 
AGRICULTURAL  EXPERIMENT  STATION 

S.  B.  DOTEN,  Director 


Bulletin  No.  99 


RENO,  NEVADA 


December,  1920 


To  diminish,  suffering  and  loss  among  domestic  animals 


THE  NARROW-LEAVED  MILKWEED 

(Asclepias  Mexicana) 

and 

THE  BROAD-LEAVED  OR  SHOWY  MILKWEED 

(Asclepias  speciosa) 

PLANTS  POISONOUS  TO  LIVE  STOCK  IN  NEVADA 

By 

C.  E.  FLEMING  and  N.  F.  PETERSON 
Of  the  Department  of  Range  Management 

Assisted  by 

M.  R.  MILLER 
Of  the  Department  of  Chemistry 

and 

DR.  L.  R.  VAWTER  and  DR.  L.  H.  WRIGHT 
Of  the  Department  of  Veterinary  Science 


PUBLISHED  BY  THE  UNIVERSITY  OF  NEVADA 
RENO,  NEVADA 


1s2 


Printed  at  the 

STATE  PRINTING  OFFICE — JOE  FARNSWORTH,  SUPERINTENDENT 
CARSON  CITY,  NEVADA 


M  5F  ^ 


NEVADA  AGRICULTURAL  EXPERIMENT  STATION 


BOARD  OF  CONTROL 

Hon.  A.  E.CHENEY  (1921)         .        .        . Reno 

Hon.  B.F.CUBLEB  (1921) Elko 

Hon.WALTERE.  PRATT  (1925) Reno 

Hon.  Mrs.  W.  H.  HOOD  (1927) Reno 

Hon.  MILES  E.  NORTH  (1929) Reno 

OFFICERS 

WALTER  E.  CLARK,  Ph.D .        .   President  of  University 

CAROLYN  BECKWITH .        .        .   Secretary 

CHARLES  H.  GORMAN Comptroller 

STAFF 

SAMUEL  B.  DOTEN,  M.A Director  and  Entomologist 

F.  L.  BIXBY,  C.E Irrigation 

(In  cooperation  with  Bureau  of  Public  Roads,  U.  S.  D.  A.) 

GEO.  HARDMAN,  M.S Assistant  in  Irrigation 

CHARLES  E.  FLEMING,  B.S.A.    ......  Range  Management 

EDWARD  RECORDS,V.M.D. Veterinarian 

STEPHEN  LOCKETT,V.M.D .      Assistant  Veterinarian 

LYMAN  R.VAWTER,  D.V.M Pathologist 

MADGE  L.  FINK,  B.A.          ....       Secretary  to  Veterinary  Department 

M.  R.  MILLER,  B.S Chemist 

MARTHA  RYAN  .  .        .       Librarian  and  Secretary  to  Director 


Agric.- Forestry.  Main  Library 


S! 

^•t 

STUDIES  OF  POISONOUS  PLANTS  IN  THE   UNIVERSITY 

OF    NEVADA 


In  recent  years,  as  the  forage  on  the  open  public  range  in  Nevada  has 
become  more  and  more  depleted,  losses  of  sheep  and  cattle  from  poison- 
ous plants  have  steadily  increased.  However,  even  the  stockmen  and 
herders  themselves  do  not  know  fully  just  which  plants  are  poisonous 
nor  how  to  avoid  them. 

The  Nevada  Agricultural  Experiment  Station  has  therefore  under- 
taken a  study  of  the  poisonous  plants  of  the  sheep  and  cattle  ranges. 
The  experimental  work  is  of  a  simple  character,  consisting  largely  of 
practical  feeding  tests.  The  plants  are  brought  to  the  University  fresh 
from  the  ranges  and  are  fed  to  common  range  live  stock  in  small  corrals. 
The  symptoms  of  poisoning  are  recorded;  and  after  the  death  of  the 
animal  the  carcass  is  cut  up  and  the  organs  are  removed  and  studied. 

An  attempt  is  also  made  to  isolate  the  active  poisonous  principle  of 
the  plant  by  suitable  chemical  methods  and  to  determine  its  chemical 
nature. 

These  experiments  are  showing  clearly  which  range  plants  are  dan- 
gerous, what  part  of  the  plant  is  poisonous,  and  at  what  season  of  the 
year  it  must  be  avoided.  They  are  also  showing  us  that  many  suspected 
plants  are  harmless,  while  others  which  are  considered  harmless  are  in 
reality  deadly. 

In  all  these  experiments  it  is  our  purpose  first  to  obtain  exact 
information  concerning  the  poisonous  range  plants  and  then  to  spread 
it  far  and  wide  among  the  stockmen  of  the  West  in  the  hope  of 
diminishing  suffering  and  loss  among  western  sheep  and  cattle. 

S.  B.  DOTEN, 
Director,  Nevada  Agricultural  Experiment  Station. 

November  1,  1920. 


487663 


SECTION    I 
The  Milkweeds  as  Plants  Poisonous  to  Live  Stock  in  Nevada 


SUMMARY 

(1)  There  are  two  common  milkweeds  in  Nevada,  both  of  which  are 
poisonous  to  sheep  and  cattle. 

(2)  One  is  a  slender,  erect,  branching  weed  with  long,  narrow,  dark- 
green  leaves,  small  flowers,  and  slender  pods.     The  other  is  a  tall  and 
fleshy  weed  with  large,  broad,  light-green  leaves,  coarse  flowers,  and 
thick  rough  pods. 

(3)  Both  kinds  grow  in  fairly  moist  places,  along  irrigation  ditches, 
by  fences  and  on  stream  banks,  on  roadsides,  and  in  patches  in  damp 
pastures. 

(4)  In  the  autumn  the  pods  break  open  and  release  quantities  of 
flat  browrn  seeds,  each  of  which  bears  a  tuft  of  shining  silky  hairs, 
lighter  than  thistledown.    The  seeds  are  carried  far  by  wind  and  water. 
Once  established,  the  plant  spreads  locally  by  means  of  its  underground 
stems. 

(5)  Animals  poisoned  by  the  narrow-leaved  milkweed  become  dull 
and  stupid  within  a  few  hours.     They  walk  about  with  a  wobbling, 
unsteady  gait,  finally  losing  all  control  over  the  muscles  of  the  legs, 
and  falling  or  lying  down.     After  the  animal  is  down,  it  has  spasms 
at  short  intervals  in  which  the  legs  are  extended  rigidly.     The  heart 
beats  at  an  increasingly  rapid  rate ;  the  animal  pants  and  grunts.    The 
head  is  drawn  sharply  back.     The  attack  may  last  for  twenty-four 
hours  and  end  with  either  the  death  or  the  recovery  of  the  animal.    If 
it  recovers,  it  will  be  in  a  weak  and  unsteady  condition  for  several  days. 

(6)  Animals  poisoned  by  the  broad-leaved  or  showy  milkweed  stop 
eating,  grow  dull,  and  lie  down;    the  breathing  is  irregular,  difficult, 
and  grunting.     There  are  no  spasms.     The  breathing  becomes  more 
difficult,  and  the  animals  dies  quietly. 

(7)  The  narrow-leaved  milkweed  is  far  more  deadly  than  the  broad  - 
leaved  or  showy  species. 

(8)  Two  or  three  other  milkweeds  grow  in  Nevada;    but  they  are 
neither  common  enough  nor  poisonous  enough  to  be  of  any  importance. 

(9)  When  the  narrow-leaved  milkweed  is  accidentally  cut  and  cured 
in  hay,  it  loses  its  bad  flavor,  but  keeps  its  deadly  character,  thus 
becoming  far  more  dangerous  than  when  fresh  and  green.     Even  the 
dead  and  dried  leaves,  left  standing  in  a  field  from  the  summer  before, 
are  poisonous  in  midwinter. 

(10)  It  is  a  costly  and  difficult  matter  to  get  rid  of  the  narrow-leaved 
milkweed  on  even  a  small  piece  of  ground.    If  a  bit  of  the  underground 
stem  is  left  in  the  soil,  it  will  soon  produce  a  new  plant. 

(11)  Both  of  our  poisonous  milkweeds  have  so  unpleasant  a  flavor 
that  neither  sheep  nor  cattle  will  eat  them  except  when  they  are  very 
hungry  and  there  is  practically  nothing  else  in  the  field  for  them  to  eat. 

(12)  Poisoning  may  be  prevented  by  keeping  hungry  animals  and 
animals  in  poor  condition  away  from  milkweed  patches,  and  by  stock- 
ing pastures  lightly  enough  to  keep  the  animals  constantly  provided 
with  other  food. 


Figure  1 — Flowers  and  Pods  of  the  Narrow-Leaved  Milkweed. 


OUR  WESTERN  MILKWEEDS 

For  many  years  several  kinds  of  milkweed  have  been  looked  upon 
with  suspicion  or  considered  poisonous  by  western  stockmen.  This 
opinion  was  based  largely  on  their  own  field  observations;  and  little 
or  no  experimental  work  has  been  done  with  any  of  the  species  except 
the  whorled-leaved  milkweed  (Asclepias  galioides).  The  latter  plant 
has  been  carefully  studied  by  ,the  Colorado  Experiment  Station,  which 
was  the  first  of  the  western  stations  to  show  that  sheep  may  be  poisoned 
by  this  plant  when  it  is  eaten  either  green  or  dry.  (See  Bulletins  246 
and  255,  Colorado  Agricultural  Experiment  Station.)  Later,  C.  D. 
Marsh  and  his  associates  of  the  Federal  Bureau  of  Plant  Industry  pub- 
lished the  results  of  their  study  of  the  same  species.  (See  Bulletin 
No.  800,  U.  S.  Department  of  Agriculture.) 

In  the  spring  of  1918  the  attention  of  the  Nevada  Experiment  Station 
was  first  called  to  our  local  milkweeds  as  plants  dangerous  to  live  stock 
when  several  lambs  died  after  eating  the  tender,  juicy  young  growth 
of  the  showy  milkweed  (Fig.  4).  Since  that  time  the  Nevada  Station 
has  tested  the  milkweeds  by  conducting  a  long  series  of  experiments 
in  which  the  plants  were  fed  to  both  sheep  and  cattle.  More  work  was 
done  with  the  narrow-leaved  milkweed  than  with  any  of  the  others 
because  it  seemed  to  be  our  most  dangerous  species.  The  result  of  these 
feeding  tests,  together  with  field  observations,  are  presented  in  this 
bulletin. 

Classes  of  Live  Stock  Poisoned  and  the  Extent  of  Losses  in  this  State  and 
Elsewhere. 

Both  feeding  tests  and  field  observations  have  shown  that  the  narrow- 
leaved  milkweed  (Asclepias  Mexicana)  is  poisonous  to  sheep  and  cattle. 
No  feedings  of  any  species  of  milkweed  have  been  made  to  horses 
because  there  seems  to  be  nothing  to  show  that  horses  have  been 
poisoned  by  these  plants. 

Because  of  the  limited  time  since  the  milkweeds  were  recognized  as 
poisonous  to  live  stock  in  Nevada,  the  extent  of  losses  cannot  be  accu- 
rately estimated.  Further,  unless  especially  large  losses  take  place, 
they  are  usually  not  reported  to  the  Experiment  Station.  However, 
because  of  the  widespread  distribution  of  the  narrow-leaved  milkweed 
and  the  ease  with  which  it  kills,  it  is  reasonable  to  assume  that  losses 
of  live  stock,  at  least  in  small  numbers,  are  constantly  caused  by  this 
common  poisonous  plant. 

In  other  States,  notably  Colorado,  Utah,  and  New  Mexico,  it  has 
been  proven  that  the  whorled-leaved  milkweed  has  caused  the  death 
of  many  sheep. 

Kinds  of  Milkweed  Dangerous  to  Live  Stock  in  Nevada. 

Several  kinds  of  milkweed  grow  in  Nevada  but,  from  the  stockman's 
point  of  view,  the  narrow-leaved  species  is  by  far  the  most  important. 
The  other  kinds  will  be  discussed  briefly  toward  the  end  of  this  bulletin. 
They  are:  the  Showy  Leaved  Milkweed  (Asclepias  speciosa)  ;  the 
Heart-Leaved  Milkweed  (Asclepias  cordifolia)  ;  and  the  Prostrate  Milk- 
weed (Asclepias  cryptoceras) .  Our  experiments  seem  to  show  that  the 
heart-leaved  and  prostrate  milkweeds  are  not  poisonous  enough  or 
common  enough  to  be  dangerous  on  the  range  or  in  pastures  in  Nevada. 


10  

General  Description  of  the  Milkweeds. 

The  milkweeds  are  usually  erect  plants,  little  if  at  all  branched,  vary- 
ing in  height  from  one  to  several  feet.  The  roots  live  over  from  year 
to  year,  sending  up  new  stems  each  season.  The  flowers  are  light- 
colored,  white  tinged  with  green  or  pink;  they  grow  in  rounded  clus- 
ters, each  flower  stalk  arising  from  the  end  of  the  stalk  of  the  cluster. 


Figure  2 — Pods  and  Seeds  of  the  Narrow-Leaved  Milkweed. 

Each  flower  has  five  cup-like  structures  (hoods),  inside  of  which  there 
is  a  horn. 

The  flowers  fall  and  are  followed  by  seed  pods  from  one  to  three 
inches  long  which  open  along  one  side  when  dry  to  .allow  the  seeds  to 
escape.  The  seeds  are  reddish-brown  and  flat;  on  one  end  there  is 


11 

a  tuft  of  long,  white,  silky  hairs  by  which  they  are  blown  about.  The 
roots  of  the  milkweeds  are  somewhat  brittle,  whitish  and  thickened; 
this  is  especially  true  of  the  showy  milkweed  (Fig.  4).  The  growth  of 
the  root  is  mainly  horizontal,  as  is  shown  in  Fig.  5 — The  Root  of  the 
Narrow-Leaved  Milkweed.  Sometimes,  however,  the  roots  penetrate 
the  soil  like  the  roots  of  alfalfa. 

The  milkweeds  have  a  milky  sap  or  juice  which  gives  to  them  their 
common  name  and  distinguishes  them  from  most  other  plants.  How- 
ever, a  milky  sap  is  found  in  many  other  plants,  such  as  the  Mexican 
poppy,  the  dandelion  and  its  close  relatives,  the  wild  lettuce,  spurges, 
and  dog-banes.  From  all  these  plants  having  a  milky  juice,  the  milk- 
weeds may  be  distinguished  by  the  following  differences :  (1)  the  Mexi- 
can poppy  is  spiny,  while  the  milkweeds  are  not ;  (2)  the  dandelion  and 
its  near  relatives  have  no  erect  stem,  while  the  milkweeds  have;  (3) 
the  general  appearance  of  the  wild  lettuce  is  quite  different  from  the 
milkweeds  and  its  flower  and  flower  clusters  (heads)  are  like  tiny  dan- 
delions and  not  at  all  like  the  flower  or  flower  clusters  of  the  milkweed ; 

(4)  the  spurges  (Euphorbia)  are  mostly  low,  branching  plants  with 
small  leaves,  the  two  halves  of  which  are  different  in  shape  and  size ; 

(5)  some  of  the  dog-banes  might  easily  be  mistaken  for  the  narrow- 
leaved  milkweed,  but  they  branch  more  freely  and  tend  to  be  bushy, 
at  least  toward  the  top.    Their  flowers  are  not  scattered  in  dense  clus- 
ters and  do  not  have  hoods  as  in  the  milkweed.     The  pods  are  similar 
to  those  of  the  milkweed  but  more  slender;   the  seeds  are  also  similar 
but  smaller  and  not  so  flattened. 

How  to  Distinguish  the  Narrow-Leaved  Milkweed  from  the  Showy  Milkweed. 

The  showy-leaved  milkweed  is  quite  abundant  in  Nevada,  but  it  is 
not  nearly  so  poisonous  as  the  milkweed  with  the  long  narrow  leaves. 
The  two  are  easily  distinguished  by  the  following  differences:  (1)  the 
narrow-leaved  milkweed  has  several  leaves  at  each  joint  of  the  stem, 
while  the  shown  species  has  but  two;  (2)  the  leaves  of  the  showy  milk- 
weed are  much  broader,  from  one-third  to  one-half  as  broad  as  they 
are  long;  (3)  the  narrow-leaved  milkweed  has  smooth  pods,  while  the 
showy  species  has  pods  roughened  by  projections.  Figures  3  and  4 
show  the  general  appearance  and  characteristics  of  these  two  plants. 

Where  the  Milkweeds  Grow. 

The  milkweeds  are  widely  distributed  in  Nevada.  They  require 
fairly  wet  soil,  and  do  not  grow  on  the  drier  parts  of  the  range.  They 
are  common  along  irrigation  ditches  and  streams,  along  roadsides,  and 
in  pastures  and  washes  and  idle  lands  which  have  not  been  cultivated 
for  a  number  of  years.  In  such  locations  the  narrow-leaved  kind  is 
more  abundant.  It  has  a  wider  distribution  than  the  showy  milkweed 
or  any  of  the  other  species  found  in  this  State. 

The  milkweeds  usually  grow  in  full  sunlight,  although  they  may  be 
found  in  partly  shaded  places  as  in  orchards  and  among  willows  and 
cottonwoods  along  streams. 

In  several  places  in  Nevada  the  narrow-leaved  milkweed  has  been 
reported  to  be  getting  more  abundant.  Especially  is  this  true  along 
the  banks  of  irrigation  ditches.  Wherever  irrigation  systems  have  been 
extended  to  new  ground,  this  poisonous  weed  soon  grows  abundantly 
along  the  ditch  banks. 


12 


Figure  3— The  Narrow-Leaved  Milkweed. 


Figure  4 — The  Broad-Leaved  or  Showy  Milkweed. 


14  

All  our  observations  indicate  that  after  it  is  once  established  the 
narrow-leaved  milkweed  tends  to  remain  confined  to  the  ditch  banks 
and  adjoining  moist  areas.  There  seems  to  be  little  danger  of  its  estab- 
lishing itself  throughout  the  alfalfa  fields  and  meadow  hay  lands  to 
such  an  extent  that  it  would  cause  the  hay  to  be  discriminated  against 
for  feeding  purposes. 

How  the  Milkweeds  Spread. 

The  milkweeds  produce  quantities  of  flat  brown  seeds,  each  of  which 
bears  a  tuft  of  shining  silky  hair  by  means  of  which  it  floats  on  the 
wind  and  is  carried  to  considerable  distances.  Often  they  are  blown 
into  irrigation  ditches  and  carried  to  distant  fields  by  the  water. 

New  patches  may  start  from  seeds,  or  from  pieces  of  roots  carried 
by  plows  and  other  farm  implements  or  picked  up  by  the  water  and 
transported  to  new  areas. 

Where  the  plant  has  become  established,  the  size  of  the  patch  is 
usually  increased  by  the  shallow  horizontal  underground  stems  which 
give  rise  to  new  plants. 


Figure  5 — Root  of  the  Narrow-Leaved  Milkweed. 


It  is  not  uncommon  for  the  same  root  system  to  connect  up  a  large 
number  of  plants,  all  of  which  were  produced  by  the  spreading  hori- 
zontal roots  of  a  mother  plant.  Thus  when  it  once  becomes  established 
it  is  indeed  hard  to  get  rid  of  this  poisonous  weed  because  of  the 
budding  of  the  roots.  In  some  of  the  milkweeds  such  buds  are  known 
to  form  as  much  as  two  feet  below  the  surface  of  the  ground ;  and  a 
two-inch  piece  of  the  root  of  the  common  milkweed  was  found  by  A.  S. 
Hitchcock  in  Kansas  to  be  able  to  form  a  new  plant.  On  small  areas 
in  Nevada  the  narrow-leaved  milkweed  has  been  dug  and  pulled  two 
or  three  times  during  the  season  without  completely  eradicating  the 
plant,  because  of  its  ability  to  produce  new  plants  from  small  pieces 
of  root  left  in  the  soil.  Thus  any  means  by  which  the  root  is  broken 
up  into  small  pieces  and  left  in  the  ground  will  enable  the  plant  to 
maintain  itself  and  in  some  instances  actuallv  to  increase. 


15 


THE  NARROW-LEAVED  MILKWEED  (Asclepias  Mexicana) 
The  Part  of  the  Plant  Which  Is  Poisonous. 

In  our  experiments  we  have  fed  the  whole  top  of  the  plant,  stems, 
leaves,  and  sometimes  flowers  and  seed  pods.  A  few  feedings  were  made 
of  leaves  only,, and  these  few  tests  seem  to  indicate  that  fee  leaves  are 
the  most  poisonous  part  of  the  plant.  The  pods  appear  to  be  less 
poisonous  than  either  the  leaves  or  the  stem.  Feeding  of  seeds  alone 
produced  no  symptoms.  This  indicates  that  the  plant  is  not  more 
dangerous,  but  perhaps  less  so,  when  it  is  full  of  seed  pods  than  at 
other  times.  For  all  practical  purposes  the  entire  plant  may  be 
considered  poisonous. 

The  Time  of  the  Year  When  It  Is  Poisonous. 

So  far  as  known  the  narrow-leaved  milkweed  is  poisonous  at  all 
stages  of  growth.  Our  tests  showed  it  to  be  poisonous  when  fed  (1)  in 
a  green  condition,  (2)  after  being  cut  and  dried  as  hay,  and  (3)  as  it 
dries  naturally  in  the  field  in  the  fall.  Thus  in  all  stages  it  is  poison- 
ous; and  hay  containing  any  large  amount  of  this  plant  may  be 
regarded  as  extremely  dangerous. 

Amount  Necessary  to  Make  Sick  or  to  Kill. 

We  fed  the  narrow-leaved  milkweed  to  cattle  and  sheep,  (1)  in  a 
fresh  green  state,  (2)  after  being  cut  and  dried,  and  (3)  as  it  cured 
naturally  on  the  stems  in  the  fall,  (4)  the  pods  alone,  and  (5)  the  seeds 
alone. 

TABLE  I 
The  Narrow-Leaved  Milkweed — The  Fresh  Green  Plant  Fed  to  Sheep 


Animal 
No. 

Weight 
Ibs. 

Date  fed 

Time  fed 

Amount 
fed,  Ibs. 

Time  symptoms 
observed 

Time  o'f  death 
or  recovery 

Final  result 

2 

120 

5-31-18 

2*25  p.  m 

, 

.     _  .Negative 

28 

63 

5-31-18 

2-30  p  m 

i 

Negative 

18 

95 

6-  8-18 

4:00  p.  m 

I 

Negative 

25  

74 

93 

98 

6-  8-18 
8-12-20 

4:05  p.  m 
4*05  p  m 

j 

6-  9—7:15  a.  m. 

6-  9—6:00  p.  m. 

Recovery 

Negative 

75 

90 

8  12  20 

4'10  p  m 

i 

Negative 

78  
72  
19  
8  
79  
8  
6 

87 
93 
68 
72 
95 
100 
65 

8-12-20 
8-12-20 
5-29-18 
5-31-18 
8-11-20 
8-12-20 
5-31-18 

4:15  p.  m 
4:40  p.  m 
4:10  p.  m 
2:40  p.  m 
4:10  p.  m 
4:20  p.  m 
2-45  p.  m 

2 
1 
1 
1 
1 
1* 

8-13—7:00  a.  m. 
8-13—8:00  a.  m. 
5-30—9:00  a.  m. 
6-  1—9:00  a.  m. 
8-12-8:00  a.  m 
8-13—5:00  p.  m 
6-  1  —  8:00  a.  m 

8-15—8:00  a.  m 
8-14—8:00  a.  m 
5-31—8:30  a.  m 
6-  2—9:00  a.  m 
8-13—7:00  a.  m 
8-14—8:00  a.  m 
6-  1—4:45  p.  m. 

Recovery 
Recovery 
.,  Recovery 
Recovery 
Recovery 
Recovery 
Death 

77— 
17 

88 
61 

01 

8-12-20 
5-29-18 

4:30  p.  m. 
4'10  p  m 

ll 

2 

8-13—7:00  a.  m 
6*00  p  m 

8-15—8:00  p.  m. 
Before  9'00  p.  m 

Recovery 
Death 

The  animals  were  not  watched  during  the  night,  usually  the  first  observation  being  made  at 
8  o'clock  in  the  morning.  This  is  the  reason  why,  in  this  and  the  following  tables,  under  the 
caption  Time  of  Death  or  Recovery,  "8 :  00  a,,  m."  appears  so  often.  It  records  the  condition  of 
the  animal  at  the  first  observation  made  in  the  morning. 

The  tests  summarized  in  this  table  indicate  that  ( 1 )  if  common  range 
ewes  eat  one-half  pound  or  less  no  -serious  trouble  will  follow;  (2) 
amounts  in  excess  of  one-half  pound  and  up  to  1J  pounds  will  usually 
make  the  animal  sick,  but  it  will  recover;  (3)  amounts  of  1^  pounds 
or  more  are  quite  likely  to  cause  death. 


16 


Figure  6 — Sheep  Poisoned  by  Narrow-Leaved  Milkweed. 


Figure  7 — Sheep  Poisoned  by  Narrow-Leaved  Milkweed. 


TABLE  II 
The  Narrow-Leaved  Milkweed — The  Air-Dried  Plant  Fed  to  Sheep 


Animal 
No. 

Weight 
Ibs. 

Date  fed 

Time  fed     Amount 
1  fed.ozs. 

Time  symptoms 
observed 

T^e°cfovdee?f    |    F"""—  " 

56 

Ill 

10-17-19 

8:20  a.  m.                 3 

.....                    Negative 

37 

90 

10-17-19 

10:30  a.  m.                3 

I            Negative 

59  
56 

100 
111 

10-17-19 
10-21-19 

8:40  a.  m.  i             4 
11:30  a.m.                4 

10-18—8:00  a.  m. 

10-23—8:00  a.  m.    Recovery 
Negative 

55  
57  
46  

8  

72  

112 
112 
80 
100 
85 

10-17-19 
10-21-19 
10-20-18 
8-24-20 
8-25-20 

11:45  a.  m.                5 
11:00  a.m.  >             5 
9:30  a.m.  ,             5 
2:50  a.  m.  |             6 
2:20  a.  m.                7 

10-18-8:00  a.  m. 
10-22-8:00  a.  m. 
10-20-2:00  p.m. 
8-25-8:00  a.  m. 
Not  observed 

10-19—  8  :00  a.  m     Recovery 

10-24—8:00  a.  m    i  Recovery 
10-23—8  :00  a.  m    1  Recovery 
8-26—  8  :00  a.  m    1  Recovery 
8-26—  8:00  a.  m     Death 

45 

85 

11-2C-18 

10:00  a.  m.  |             8 

11-20—2:00  p.  m. 

11-21—2:45  p.  m                     Death 

I 

1 

After  the  green  plant  has  been  thoroughly  dried  in  the  sun  it  loses 
approximately  65%  (two-thirds)  of  its  original  weight.  Its  condition 
is  then  much  the  same  as  it  would  be  if  cut  and  cured  in  hay.  In  the 
feeding  tests  the  air-dried  material  was  in  most  instances  mixed  with 
alfalfa  hay  and  fed. 


17 


The  feedings  of  hay  and  milkweed  may  be  briefly  summed  up  for 
range  ewes  as  follows:  (1)  3  ounces  may  or  may  not  make  the  animal 
sick,  (2)  4  to  6  ounces  will  usually  produce  poisoning,  (3)  amounts  in 
excess  of  6  ounces  will  probably  cause  death. 

The  dried  milkweed  is  evidently  very  poisonous.  While  the  plant  is 
green  sheep  are  very  likely  to  avoid  it  because  the  taste  is  repellent ; 
but  after  it  is  dry  it  loses  much  of  its  bad  flavor  and  is  then  more 
dangerous  because  more  readily  eaten. 

It  takes  about  three  parts  of  fresh  milkweed  to  make  one  part  of 
air-dried;  and  it  is  an  interesting  fact  that  if  the  above  amounts  of 
air-dried  material  are  multiplied  by  3  to  give  the  original  green 
weight  they  agree  very  closely  in  most  cases  with  the  results  of  Table  I. 

The  feeding  tests  given  in  Table  II  therefore  indicate  that  drying 
causes  little  if  any  loss  of  the  poisonous  principle.  Consequently  when 
this  milkweed  is  cut  and  fed  in  hay,  it  becomes  a  serious  source  of 
danger. 

TABLE  III 

The  Narrow-Leaved  Milkweed— The  Plant  Which  Had  Dried  Naturally  in  the 

Field  Fed  to  Sheep 


Animal  Weight 
No.    I     Ibs. 

Date  fed 

Time  fed 

Amount 
fed,  Ibs. 

Time  symptoms 
observed 

Time  of  death 
or  recovery 

Final  result 

48 

85 
115 
80 
84 
80 
80 

11-12-19 
11-29-19 
12-  9-19 
12-16-18 
12-26-18 
1-  2-19 

2:30  p.  m. 
1:50  p.m. 
9:00  a.  m. 
10:45  a.  m. 
11:30  a.  m. 
2:00  p.  m. 

1 

ii 

Negative 

58 

11-30—8:00  a.  m. 
12-  9—2:45  p.  m. 
12-17—8:00  a.  m. 
12-27—8:00  a.  m. 
1-  2—9:00  p.  m. 

12-  2—8:00  a.  m. 
12-10-8:00  a.  m. 
12-18—8:00  a.  m. 
12-30—8:00  a.  m. 
1-  3—3:00  p.  m. 

Recovery 

43 

Recovery 

45 

Recovery 
Recovery 

43 

43  

__i  Death 

The  plants  which  were  used  in  the  above  feeding  tests  were  collected 
in  late  autumn  after  they  had  fully  matured  and  become  dry.  The 
feedings  were  made  in  the  months  of  November,  December,  and  Janu- 
ary. The  results  may  be  summed  up  briefly  as  follows:  (1)  small 
amounts  up  to  3  ounces  are  not  dangerous,  (2)  amounts  from  5  to  16 
ounces  will  usually  produce  poisoning,  (3)  amounts  in  excess  of  16 
ounces  are  extremely  dangerous,  and  are  likely  to  cause  death. 

Comparing  the  results  given  in  Table  I  with  those  of  Table  III,  it 
is  found  that  it  takes  about  as  much  of  the  naturally  cured  material, 
dry  weight,  to  cause  death  as  of  the  fresh  green  plant.  From  this  it 
appears  that  some  of  the  poison  is  destroyed  or  lost  when  the  dried 
plant  stands  exposed  to  snow  and  rain  after  the  leaves  are  dead. 

During  the  fall  and  winter  months  the  dried  plants  may  be  found 
still  standing.  Other  feed  is  usually  very  short  and  scarce  at  that  time 
of  the  year;  and  the  narrow-leaved  milkweed,  still  retaining  a  con- 
siderable part  of  its  original  poison,  is  then  a  source  of  danger  to 
grazing  animals. 

TABLE  IV 
The  Narrow-Leaved  Milkweed — Seeds  Fed  to  Sheep 


Animal 
No. 

Weight 
Ibs. 

Date  fed 

Time  fed 

Amount    Time  symptoms 
fed,  ozs.          observed 

Time  of  death 
or  recovery 

Final  result 

58-.. 
59  

98 
101 

9-7-19 
9-7-19 

3:30  p.  m. 
3:40  p.  m. 

I 

Negative 

Negative 

18 


In  late  summer  and  early  fall  the  narrow-leaved  milkweed  has  a 

large  number  of  seeds  and  pods. 
In  previous  feeding  tests  the  pods 
and  seeds  of  the  showy  milkweed 
were  found  to  be  the  most  poison- 
ous part  of  the  plant ;  so  it  was 
thought  that  this  might  also  be 
true  of  the  narrow-leaved  milk- 
weed. Two  feedings  of  seeds  were 
made,  one  of  2  ounces  and  the  other 
of  5  ounces.  Neither  animal  was 
poisoned.  The  quantity  of  seed 
which  we  fed  in  either  test  repre- 
sents the  seed  production  from  a 
large  number  of  plants,  a  number 
in  excess  of  what  it  is  believed  any 
animal  would  be  able  to  get  within 
a  reasonable  length  of  time.  Con- 
sequently it  seems  that  the  danger  of  poisoning  from  these  seeds  is  very 
slight  and  that  such  poisoning  is  highly  improbable. 


Figure  8  —  The  First  Symptoms 
of  Poisoning  by  Narrow-Leaved 
Milkweed. 


TABLE  V 

The  Narrow-Leaved  Milkweed — Green  Pods  Fed  to  Sheep 


Animal 
No. 

Weight 
Ibs. 

Date  fed 

Time  fed 

Amount 
fed,  Ibs 

Time  symptoms 
observed 

Time  of  death 
or  recovery 

Final  result 

73 

77 

8-17-20 

4:20  p.  m 

§ 

Negative 

74 

98 

8-17-20 

4-35  p.  m 

1 

Negative 

g 

100 

8-17-20 

4:50  p.  m 

2 

Negative 

69  
8 

80 
100 

8-19-20 
8^19-20 

7:40  a.  m 
7:30  a.  m 

2i 

3| 

8-20-7:00  a.  m. 

8-22—8:00  a.  m. 

Recovery 
Negative 

Five  feedings  of  green  pods  were  made,  using  amounts  of  from  one- 
half  to  3i|  pounds.  None  of  these  feedings  caused  poisoning  with  the 
exception  of  one  2J-pound  feeding.  These  tests  indicate  that  the  pods 
are  less  poisonous  than  the  leaves  and  stems,  and  that  the  danger  of 
loss  is  smaller  when  the  -plant  is  full  of  pods. 


TABLE  VI 

The  Narrow-Leaved  Milkweed — The  Dried  Plant  Fed  on  Successive 
Days  to  Sheep 


Animal 
No. 

Weight 
Ibs. 

Date  fed 

Time  fed 

Amount 
fed,  ozs. 

Time  symptoms 
observed 

Time  of  death 
or  recovery 

Final  result 

37 

85 

10-21-19 

11:45  a.  m. 

2 

Negative 

10-22-19 

11:15  a.m. 

2 

10-23-19 

10:30  a.  m. 

2 

Negative 

10-24-19 

10:00  a.  m. 

2 

10-25-19 

7:30  a.  m. 

2 

Negative 

10-26-19 

11:00  a.  m. 

2 

Negative 

10-27-19 

8:30  a.  m. 

3 

Negative 

10-28-19 

10:00  a.  m. 

3 

Negative 

10-29-19 

10:00  a.  m. 

4 

Negative 

10-31-19 

11:30  a.  m. 

5 

11-  2—  7~:0b  a.  m. 

11-  3—8:00  a.  m. 

Recovery 

Dry  material  collected  September  6.    Sheep  never  very  sick. 


59 


93 


10-27-19 
10-28-19 
10-29-19 
10-31-19 


11:10  a.m. 
8:30  a.m. 
11:00  a.  m. 
10:30  a.  m. 


10-31-2:00  p.m. 


-.__. j Negative 

! Negative 

± I Negative 

11-  2— 7:30  a.  m.  I .Recovery 


Dry  material  collected  September  6.     Sheep  only  slightly  sick. 


19 


TABLE  VI— Continued 


Animal  Weight 
No.     ;     Ibs. 

Date  fed 

Time  fed 

Amount 
fed,  ozs. 

Time  symptoms 
observed 

Time  of  death 
or  recovery 

Final  result 

59  

90 

11-  3-19 

11-  8-19 
11-12-19 

10:30  a.  m. 
11:30  a.  m. 
2:00  D.  m. 

7 
6 

11-  3—5:00  p.  m. 
11-  9—7:00  a.  m. 
11-15  (dull) 

11-  6—8:00  a.  m. 
11-10—8:00  a.  m. 
11-15—8:00  a^m. 

Recovery 
Recovery 

...Recovery 

Material  collected  as  it  had  dried  in  the  field.    Sheep  quite  sick. 


lOa  .... 

100 

7-21-19 
7-22-19 

9:00  a.  m. 
10:25  a.  m. 

2 
2 

7-22—12  m. 

7-23—10:00  a.  m. 

Death 

120  

95 

7-21-19 
7-22-19 

9:30  a.  m. 
10-25  a  m 

2 
2 

Negative 

• 

When  animals  are  poisoned  with  the  narrow-leaved  milkweed  they 
are  affected  for  a  considerable  time,  the  poison  appearing  to  be  elimi- 
nated slowly.  Because  of  this  slow  recovery  it  was  thought  that  small 
amounts  fed  daily  might  cause  an  accumulation  of  the  poisonous  prin- 
ciple in  the  animal. 

Ewe  37  was  fed  daily  2  ounces  of  sun-dried  milkweed  for  six  days 
without  showing  any  symptoms  of  poisoning.  The  dose  was  then 
increased  to  3  ounces  for  two  days.  On  the  following  day,  4  ounces 
were  fed  without  causing  any  symptoms,  and  two  days  later  she  was 
fed  5  ounces  and  became  only  slightly  sick.  During  the  ten-day  period 
she  had  been  fed  a  total  of  27  ounces ;  yet  it  was  only  on  the  last  day, 
when  she  was  fed  5  ounces,  that  she  showed  any  signs  of  poisoning.  In 
all  the  tests  summarized  in  Table  II  the  feedings  of  5  ounces  produced 
symptoms  of  poisoning.  These  successive  feeding  tests  of  Table  VI 
indicate  very  clearly  that  there  is  little  if  any  cumulative  action  when 
the  milkweed  is  fed  at  brief  intervals. 

Sheep  59,  which  had  been  made  very  sick  with  4  ounces  in  an  earlier 
experiment,  was  fed  2  ounces  daily  for  two  days ;  then  4  ounces  were 
fed  without  producing  any  symptoms.  Two  days  later,  when  again 
fed  4  ounces,  this  animal  was  made  slightly  sick.  This  feeding  test 
also  indicates  that  there  is  no  cumulative  action  when  small  doses  are 
fed  on  consecutive  days. 

Three  days  later,  on  November  3,  Sheep  59,  the  same  animal  as 
mentioned  above,  was  fed  6  ounces  of  the  sun-dried  milkweed,  which 
made  it  quite  sick.  Five  days  later  it  was  fed  7  ounces  and  again  it 
developed  symptoms  of  poisoning.  Finally,  on  November  12,  four  days 
later,  7  ounces  were  fed,  the  animal  again  becoming  slightly  sick.  Each 
of  these  feedings  made  the  animal  sick,  but  not  nearly  so  sick  as  the 
original  4  ounces.  The  last  three  feedings  were  made  with  a  different 
lot  of  milkweed  material  which  may  have  been  less  poisonous ;  although 
when  5  ounces  of  this  lot  was  fed  to  another  ewe  it  made  her  sick  for 
two  days. 

Animal  lOa  died  when  given  the  second  feeding  of  2  ounces.  This 
case  can  hardly  be  considered  as  at  all  typical  because  the  animal  was 
found  to  have  a  badly  diseased  kidney  which  may  have  retarded  the 
elimination  of  the  poison  and  hastened  death. 

Sheep  120,  when  fed  the  same  amounts  and  in  a  similar  way  as 
Sheep  lOa,  developed  no  poisoning  symptoms  and  to  all  outward 
appearances  was  normal. 

These  tests  prove  rather  clearly  that  there  is  no  cumulative  action  of 
the  poisonous  principle  in  sheep.  The  same,  it  is  believed,  will  hold 
true  for  other  animals.  Rather,  they  seem  to  show  that  there  is  a 


20  

tendency  to  develop  tolerance  for  the  poison.  It  may  be  that  the  slow 
recovery  is  due  more  to  the  slowness  with  which  the  nervous  system 
recovers  from  the  action  of  the  poison  than  to  the  poison  being  retained 
in  the  system. 

TABLE  VII 
The  Narrow-Leaved  Milkweed — The  Green  Plant  Fed  to  Cattle 


Animal 
No. 

Weight 
Ibs. 

Date  fed 

Time  fed 

Amour 
fed,  Ib 

15— 

260 

8-11-20 

8:00  a.  m. 

1 

19  

270 

8-14-20 

11:10  a.  m. 

li 

15  

260 

8-13-20 

4:15  p.m. 

2 

19-  — 

270 

8-16-20 

2:50  p.m. 

2k 

20  

320 

8-14-20 

2:30  p.m. 

3 

9  

225 

8-  9-19 

10:00  a.m. 

81 

888  

211 

7-23-19 

8:30-11:30 

4i 

7  

195 

8-12-19 

4:00  p.m. 

5 

Amount  j  Time  symptoms  j    Time  of  death     j     Final  result 
observed  or  recovery 


f 

.  Negative 

Negative 

Negative 

8-17  —  7-00  a  m 

8-17  —  11  '40  a  m 

Death 

8-15—  8:00  a.  m. 
8-10—  8:00  a.  m. 
7-23—  1:00  p.  m. 
8-12  —  10*00  p  m 

8-18—  8:00  a.  m 
8-11—  4:00  p.  m 
7-25—  8:00  a.  m 
8-13—  10*00  a  m 

Recovery 
Recovery 
Recovery 
Death 

The  foregoing  table  made  from  tests  with  yearling  animals  may  be 
briefly  summarized  for  a  stockman's  use  as  follows:  (1)  amounts 
below  2  pounds  are  not  ordinarily  dangerous;  (2)  amounts  in  excess 
of  2  pounds  and  up  to  5  pounds  are  dangerous;  (3)  amounts  of  5 
pounds  or  more  may  be  reasonably  certain  of  causing  death;  (4)  there 
is  a  wide  variation  in  the  susceptibility  of  individual  animals,  some 
being  poisoned  with  less  amounts  than  others. 

TABLE  VIII 

The  Narrow-Leaved  Milkweed — The  Green  Pods  Fed  to  Cattle 


Animal  Weight 
No.         Ibs. 

Date  fed 

Time  fed 

Amount 
fed.  Ibs. 

Time  symptoms 
observed 

Time  of  death    |    Fin 
or  recovery 

15...              260  i 

8-16-20  ! 

1:45  p.  m. 

21 



i 

.  Negative 


This  one  feeding  showed  very  clearh'  from  the  view-point  of  a  stock- 
man that  there  is  no  increased  danger  from  an  animal  eating  pods,  for 

(1)  it  takes  a  large  number  of  the  plans  to  produce  2^  pounds  of  pods, 
a  greater  number  than  any  animal  would  graze  in  any  one  time ;  ,  and 

(2)  if  2J  pounds  produce  no  symptoms  of  poisoning,  it  is  plain  that 
the  pods  are  not  especially  poisonous. 

The  following  table  summarizes  the  feeding  of  air-dried  narrow- 
leaved  milkweed  to  cattle.  This  material  was  cut  green  and  allowed 
to  dry  thoroughly  in  the  sun;  the  weight  when  dry  being  approxi- 
mately 66%  less  than  the  green  weight: 


TABLE  IX 
The  Narrow-Leaved  Milkweed — The  Air-Dried  Plant  Fed  to  Cattle 


Animal 
No. 

Weight 
Ibs. 

Date  fed 

Time  fed 

Amount    Time  symptoms  1    Time  of  death 
fed,  Ibs.  i        observed              or  recovery 

Final  result 

48  
15  
49  
15  
8  
17  
18  
31  

272 
260 
298 
260 
225 
345 
220 
280 

9-24-20 
8-25-20 
9-15-20 
6-15-20 
10-16-19 
6-16-20 
7-21-20 
6-14-20 

10:00  a.  m 
1:00  p.  m 
9:00  a.  m 
8:00  a.  m 
4-6  p.  m 
10:00  a.  m 
5:00  p.  m. 
11:30  a.  m. 

i 
} 

I 
3 

Motra+ivp 

9-16—4:30  p.  m. 
6-15—2:30  p.  m. 
10-17—8:00  a.  m. 
6-17—8:00  a.  m. 
7-22—8:00  a.  m. 
6-14—7:00  p.  m. 

9-17—  8:00  a.  m 
6-16—  8:00  a.  m 
10-17—11:00  p.  m 
6-18—  8:00  a.  m 
7-23-  7:00  a.  m 
6-15—  7:00  a.  m 

Recovery 
Recovery 
Death 

__"  Recovery 
Death 
Death 

21  

For  the  practical  purposes  of  the  livestock  business  the  following 
conclusions  may  be  drawn  from  this  table  for  yearling  animals  weighing 
around  250  pounds:  (1)  small 
amounts  of  one-fourth  pound  or 
less  are  practically  harmless;  (2) 
amounts  of  one-half  pound  are 
dangerous  but  not  fatal;  (3) 
amounts  of  three-fourths  of  a 
pound  will  either  kill  the  animal  or 
make  it  very  sick;  (4)  all  amounts 
in  excess  of  three-fourths  of  a 
pound  are  highly  dangerous. 

Animal  31,  through  a  mistake, 
was  fed  3  pounds  of  the  dried 
plant  mixed  with  alfalfa.  The  ani- 
mal ate  this  very  greedily.  This 
shows  that  an  animal  will  readily 
eat  much  more  than  a  fatal  dose  of 
the  dry  milkweed,  especially  if  it  is 
mixed  with  a.  palatable  feed  such 
as  alfalfa  hay.  When  the  plant  is 
dried,  it  does  not  lose  its  poisonous 
character,  but  apparently  does  lose 
its  bad  flavor  and  becomes  much 
more  attractive  to  both  sheep  and 
cattle. 

SYMPTOMS    OF    MILKWEED 
POISONING 

The  first  symptom  noted  in  sheep 
is  extreme  dullness  or  entire  loss 
of  appetite.  In  as  sluggish  an  ani- 
mal as  a  sheep  this  abnormal  dull- 
ness is  often  difficult  to  detect,  and 
some  of  the  tests  recorded  as  nega- 
tive may  have  had  this  symptom.  In 
several  cases  there  was  a  distinct 
trembling  over  the  entire  body 
accompanied  by  salivation.  The 
next  symptom  to  appear  was  a  wob- 
bly unsteady  gait,  first  noticeable 
in  the  hind  legs.  In  several  cases 
this  became  worse  until  the  animal 
staggered  and  was  hardly  able  to 
walk,  sometimes  falling  over. 

In  extreme  cases  this  would  be 
followed  by  a  stage  where  the  ani- 
mal was  down  and  unable  to  get 
up.  Some  of  the  animals  while 
down  were  in  a  comatose  stage  as 
if  asleep  or  in  deep  stupor. 

In  the  fatal  cases  there  was  a 


Figure  9 — Calf  Poisoned  by  Narrow- 
Leaved  Milkweed. 


series  of  spasms  while  the  animal  was  down,  much  resembling  the 
symptoms  of  water  hemlock  (poison  parsnip,  Cicuta)  poisoning.    While 


22  

t 

in  this  condition  the  eyes  were  staring  and  bleared,  the  pupils  dilated. 
The  head  was  drawn  far  back ;  in  many  cases  there  was  champing  of 
the  jaws  and  grating  of  the  teeth,  with  rapid  running  or  kicking  move- 
ments of  both  the  hind  and  front  legs,  followed  by  spells  when  the 
legs  would  be  extended  and  rigid.  Any  disturbance  of  the  animal 
then  brought  on  additional  spasms,  attended  frequently  by  bleating 
grunts  or  groans.  In  all  fatal  cases  the  spasms  occurred  at  irregular 
intervals  until  death,  spasms  becoming  weaker  and  of  shorter  duration 
with  a  longer  interval  between  them. 

In  nonfatal  cases  the  symptoms  during  recovery  were  as  follows: 
If  the  animal  had  been  down,  it  would  get  up  but  be  hardly  able  to 
walk,  often  falling  down  in  its  attempt  to  keep  on  its  feet.  As  the 
animal  began  to  get  better  it  would  walk  with  a  distinctly  unsteady 
gait  and  would  sometimes  refuse  to  eat  for  a  considerable  length  of 
time.  Some  would  eat  while  still  hardly  able  to  walk.  The  symptoms 
would  disappear  so  gradually  that  it  would  often  be  very  difficult  to 
say  definitely  when  the  animals  had  recovered,  just  as  it  was  hard 
to  tell  when  they  began  to  get  sick. 

The  sheep  that  died  were  sick  from  five  to  twenty-four  hours.  Those 
that  recovered  were  sick  from  twelve  to  seventy-two  hours,  most  cases 
from  twelve  to  forty-eight  hours.  Cattle  showed  practically  the  same 
series  of  symptoms  as  did  sheep.  Those  that  died  were  sick  twelve  to 
fifteen  hours,  and  those  that  recovered  were  sick  eighteen  to  forty-two 
hours. 

Typical  Cases 

Case  No.  1 — A  sheep  weighing  100  pounds  was  fed  4  ounces  of  air- 
dried  leaves  at  8 : 40  a.  m.  on  November  17,  1919.  The  following 
morning  at  8  a.  m.  she  was  sick  and  walked  with  an  unsteady  gait.  At 
2  p.  m.  she  was  much  worse  and  was  hardly  able  to  get  up.  By  6  o'clock 
she  was  down  and  unable  to  rise.  She  lay  flat  on  her  side  and  appeared 
to  be  in  a  deep  stupor  until  2  p.  m.  of  the  20th,  when  she  got  up,  but 
walked  with  a  very  unsteady  gait  and  appeared  to  have  imperfect 
control  of  the  muscles  of  one  hind  leg.  She  was  so  weak  that  she  fell 
down,  but  soon  got  up  again.  Next  morning  she  appeared  normal, 
except  that  she  limped  on  one  hind  leg. 

Case  No.  2—  An  ewe  weighing  115  pounds  was  fed  5  ounces  of  air- 
dried  material  at  11  a.  m.  on  October  21,  1919.  By  midnight  no 
symptoms  had  appeared.  At  8  o'clock  next  morning  she  was  sick  and 
scarcely  able  to  wajk.  By  11  a.  m.  she  was  down  and  was  hardly  able 
to  get  up.  At  9  p.  m.  she  was  still  sick,  and  the  following  day  she 
staggered  around  when  she  walked.  Next  morning,  October  23,  she 
appeared  to  have  practically  recovered. 

Case  No.  3 — A  ewe  weighing  85  pounds  was  fed  8  ounces  of  dry 
leaves  at  10  a.  m.  011  November  20,  1919.  At  2  p.  m.  she  was  drooling 
freely  and  not  eating.  By  4 :  30  p.  m.  she  walked  with  an  unsteady  gait, 
this  being  especially  noticeable  in  the  hind  quarters.  She  continued  to 
get  worse,  and  at  7 :  30  p.  m.  could  hardly  get  up,  and  when  upon  her 
feet  could  walk  only  a  very  few  steps  before  she  would  fall  down.  By 
9  :  30  p.  m.  she  was  unable  to  stand.  Next  morning  at  8  o  'clock  she  was 
about  the  same  as  when  seen  at  9  :30  the  night  before.  She  made  sev- 
eral attempts  to  get  up,  but  each  time  would  fall  t>ver.  Over  the  entire 
body  there  was  a  peculiar  trembling  of  the  muscles.  At  11  a.  m.  when- 


23 

ever  disturbed  or  moved  she  went  into  convulsions.  At  2:30fp.  m. 
she  had  a  severe  convulsion,  and  died  at  2 :  45  p.  m. 

Case  No.  4 — A  ewe  weighing  65  pounds  was  fed  1£  pounds  of  green 
material  at  2 :45  p.  m.  At  8 : 40  p.  m.  she  was  sick.  When  she 
attempted  to  walk  it  was  with  a  staggering  motion.  By  8  o  'clock  next 
morning  she  was  down  on  her  side,  her  head  drawn  far  back,  eyes 
staring  and  bleared,  the  pupils  dilated.  At  times  she  would  grind  her 
teeth  and  champ  her  jaws.  Most  of  the  time  there  was  a  rapid  running 
movement  of  the  legs,  followed  by  spells  when  they  would  be  extended 
and  extremely  rigid.  This  series  of  movements  continued  until  noon. 
By  2  :30  p.  m.  the  spasms  had  become  weaker  and  of  shorter  duration, 
and  the  intervals  between  them  were  longer.  At  3 : 30  p.  m.  the 
spasms  were  very  weak,  lasting  for  an  instant  or  two  and  recurring 
about  every  ten  minutes.  The  animal's  temperature  was  then  105.6°. 
At  4  p.  m.  the  spasms  increased  in  violence,  became  more  severe  and 
were  accompanied  by  bleating  grunts.  At  4 :  15  p.  m.  there  was  a 
severe,  spasm  lasting  about  five  minutes,  accompanied  by  champing  of 
the  jaws,  grinding  of  the  teeth,  and  foaming  at  the  mouth.  The  head 
was  frequently  drawn  far  back.  These  severe  spasms  continued  about 
every  two  minutes  until  shortly  before  death,  which  occurred  at 
4  :  45  p.  m. 

The  autopsy  showed  the  spleen  slightly  mushy,  the  liver  soft  and 
friable ;  all  other  organs  appeared  normal.  (Brain  not  examined.) 

Case  No.  5 — A  ewe  weighing  80  pounds  was  fed  at  2  p.  m.  January  2, 
1919,  1^  pounds  of  material  that  had  dried  naturally  in  the  field.  By 
9  a.  m.  she  was  sick,  walked  with  an  unsteady  gait,  this  being  especially 
noticeable  in  the  hind  legs.  At  8  a.  m.  the  next  day  she  was  down  and 
unable  to  get  up,  lying  flat  on  her  side  with  legs  stretched  out.  Fre- 
quently she  would  chew  at  the  bedding,  and  would  champ  her  jaws 
most  of  the  time.  A  peculiar  trembling  of  the  nose  and  lips  was  notice- 
able. At  9 :  30  p.  m.  she  was  in  the  same  condition,  groaning  as  if  in 
pain,  kicking  the  hind  legs  and  frothing  at  the  mouth.  Her  tempera- 
ture at  1 :  30  p.  m.  was  103°.  She  was  in  this  condition  until. 3  p.  m., 
when  she  died. 

Case  No.  6 — A  sheep  weighing  100  pounds  was  fed  2  ounces  at  9 
a.  m.  July  21.  The  next  day  at  10  a.  m.  2  ounces  more  were  fed.  By 
noon  the  animal  was  sick,  walking  with  an  unsteady  gait.  It  con- 
tinued to  get  worse  during  the  afternoon.  Next  morning  it  was  unable 
to  get  up  and  had  convulsions  when  disturbed.  It  soon  fell  over  on  its 
side  and  had  running  movements  with  its  legs.  It  remained  in  this 
condition  until  death,  which  took  place  about  10  a.  m. 

The  autopsy  at  11  a.  m.  showed  the  following  conditions:  There 
was  an  acute  cloudy  swelling  of  the  right  kidney.  The  left  was  affected 
by  a  chronic  disease  not  caused  by  poisoning.  The  liver  was  fri- 
able and  highly  reddened ;  blood  flowed  from  cut  surface.  Some  of  the 
lymph  glands  were  hemorrhagic.  The  brain  showed  marked  congestion 
of  the  meninges,  especially  over  the  cerebellum  and  the  anterior  por- 
tions of  the  cerebrum.  Many  minute  pin-point  hemorrhages  were 
found  in  the  gray  matter  of  the  brain.  These  were  located  in  the  corpus 
striatum,  corpus  callosum,  medulla,  and  medullary  portions  of  the 
cerebrum. 

Case  No.  7 — A  sheep  was  fed  7  ounces  of  dry  material  at  2 :  30  p.  m., 


24 


August  25,  1920.  It  was  found  dead  next  morning  at  8  o'clock.  The 
autopsy  showed  the  following:  carcass  bloated,  pupils  dilated.  There 
was  considerable  congestion  of  the  mucous  membrane  of  the  fourth 
stomach  (abomasum)  and  small  pin-point  hemorrhages  in  the  duode- 
num. The  mucous  membrane  of  the  bladder  was  congested.  There 
was  a  cloudy  swelling  of  the  kidneys.  In  the  brain  there  was  marked 
congestion  of  the  pia  mater,  and  marked  injection  of  the  capillaries  of 
the  medulla.  Hemorrhages  were  found  in  the  gray  matter  of  the 
brain. 

Case  No.  8 — A  yearling  calf  weighing  211  pounds  was  fed  4J  pounds 
of  fresh  material  on  July  23,  1919,  between  8 :  30  and  11 :  30  a.  m.  At 
1  p.  m.  it  was  frothing  at  the  mouth,  and  its  breathing  was  rapid  and 
irregular.  These  symptoms  (perhaps  not  due  to  the  milkweed)  soon 
disappeared  and  the  animal  seemed  normal  the  rest  of  the  day.  The 
next  morning  it  walked  with  a  peculiar,  stiff  staggering  gait.  It  ate 
a  little  when  fed.  At  6  p.  m.  it  was  very  weak  and  wobbly,  much  more 
so  than  in  the  morning.  At  8  a.  m.  the  next  day  it  was  much  better, 
but  still  walked  with  a  stiff  unsteady  gait. 

_  Case    No.    9  —  A    yearling    calf 

weighing  225  pounds  was  fed  3^ 
pounds  of  green  material  at  10 
a.  m.  on  August  9,  1919.  At  8  a.  m. 
the  next  day  it  was  sick  and  hardly 
able  to  get  up.  When  on  its  feet 
it  was  very  weak  and  staggered 
about.  At  noon  it  appeared  to  be 
in  about  the  same  condition  as  in 
the  morning.  By  evening  it  was 
much  better.  Next  morning  at  8 
a.  m.  it  appeared  to  have  quite 
completely  recovered,  but  at  times 
later  in  the  day  it  staggered  some- 
what in  walking. 

Case   No.    10 — A    yearling   calf 
(195   pounds)   was   fed   5   pounds 

of  green  material  at  4  p.  m.  on  August  12,  1919.  At  10  p.  m.  it  was 
slightly  sick.  Next  morning  at  8  o'clock  it  was  very  sick  and  hardly 
able  to  walk,  staggering  and  falling  down  frequently.  Finally  it  col- 
lapsed and  lay  on  its  side,  kicking  rapidly  with  its  legs.  Death  occurred 
at  10  a.  m. 

In  the  autopsy  slight  congestion  was  found  in  the  fourth  stomach 
and  in  the  meninges  of  the  brain. 

Case  No.  11 — A  yearling  calf  weighing  255  pounds  was  fed  on  Octo- 
ber 16,  1919,  between  4  and  6  p.  m.,  three-fourths  of  a  pound  of  dry 
material,  which  was  collected  September  6  and  air-dried.  At  8  a.  m. 
next  day  it  was  sick  and  hardly  able  to  walk.  There  was  marked  inco- 
ordination  of  the  muscles  of  the  hind  legs.  At  2  p.  m.  it  was  down  on 
its  side,  with  legs  stretched  out,  head  drawn  far  back,  eyes  rolled  up ; 
the  animal  appeared  to  be  dying.  This  was  followed  by  periods  when 
it  seemed  to  be  getting  better,  but  soon  it  would  have  another  similar 
attack.  During  the  afternoon  it  had  a  series  of  such  attacks.  At  8 
p.  m.  it  was  still  down  and  unable  to  get  up.  At  midnight  it  was  found 


Figure  10 — An  Early  Stage  of 
Poisoning  by  Narrow-Leaved 
Milkweed. 


25  

dead.  The  autopsy  at  9  a.  m.  October  18  showed  slight  hemorrhages 
in  the  trachea,  lungs  hemorrhagic,  kidneys  congested;  the  heart  had 
severe  hemorrhages,  both  internally  and  externally. 

Case  No.  12 — A  yearling  calf  weighing  220  pounds  was  fed  three- 
fourths  of  a  pound  of  dry  leaves  at  5  p.  m.  July  21,  1920,  which  was  all 
eaten  next  morning.  At  8  a.  m.  the  animal  was  sick  and  walked  with 
an  unsteady  gait.  The  incoordination  was  most  marked  in  the  hind 
legs,  especially  the  left  hind  leg.  The  back  was  curved  to  the  right.  It 
kept  getting  worse  during  the  afternoon,  and  was  found  dead  next 
day  at  7  a.  m.  The  autopsy  at  9  a.  m.  showed  the  lymph  glands  hemor- 
rhagic. There  was  acute  inflammation  of  the  liver  and  of  the  bladder. 
Small  hemorrhages  were  found  on  the  heart.  The  meninges  of  the 
brain  were  congested  in  region  of  the  cerebrum.  There  were  minute 
pin-point  hemorrhages  in  the  gray  matter  of  the  brain;  these  were 
more  marked  in  the  left  side  than  in  the  right.  These  hemorrhages 
were  located  in  the  corpus  striatum  and  in  the  medullary  portion  of 
the  cerebrum  and  cerebellum. 

The  Time  of  the  Year  When  Milkweed  Is  Poisonous. 

All  the  feeding  tests  and  field  observations  clearly  indicate  that  this 
milkweed  is  poisonous  at  all  times  .of  the  year.  Animals  have  been 
poisoned  and  killed  by  plants  collected  in  the  spring  of  the  year  when 
they  were  just  a  few  inches  high,  and  by  plants  collected  at  later  stages 
of  growth  up  to  the  time  when  they  had  become  fully  matured  and 
dried  up  in  the  fall  of  the  year.  Losses,  therefore,  may  occur  at  any 
time  when  hungry  animals  feed  upon  this  milkweed. 

Prevention  of  Losses. 

There  is  no  known  remedy  for  an  animal  badly  poisoned  with  this 
plant.  Consequently,  to  avoid  losses  it  is  necessary  to  understand  the 
conditions  under  which  an  animal  is  most  likely  to  eat  a  fatal  dose. 
The  fresh  green  milkweed  as  it  grows  in  the  field  is  not  relished  by  any 
class  of  live  stock  and  is  eaten  only  under  stress  of  hunger.  This  is  not 
the  case  when  it  is  cut  and  dried  and  put  up  in  hay,  for  it  then  loses  a 
large  part  of  its  disagreeable  taste  and  is  quite  readily  eaten.  Thus  hay 
containing  this  milkweed  is  always  dangerous.  On  the  other  hand, 
ranges  or  pastures  where  this  plant  grows  are  not  always  dangerous, 
providing  there  is  enough  grass  or  other  forage  to  satisfy  the  animals. 
Thus  the  losses  occur  (1)  when  hungry  animals  are  being  herded  along 
driveways  or  trails  where  there  is  little  or  no  feed  for  stock;  (2)  when 
stock  are  pastured  on  overgrazed  or  very  closely  grazed  ranges  sup- 
porting this  plant;  (3)  when  stock  are  held  in  pastures  growing  this 
milkweed  until  all  the  valuable  forage  has  been  eaten;  and  (4)  when 
stock  are  bedded  on  areas  where  this  milkweed  is  abundant. 

Most  plants  of  a  poisonous  nature  contain  substances  which  are 
distinctly  distasteful  to  live  stock.  In  general  it  may  be  said  that  an 
animal  will  first  graze  plants  to  which  it  has  been  used  and  whose 
flavor  has  been  found  agreeable.  However,  in  the  absence  of  good 
grazing  it  will  eat  what  it  is  forced  to  eat  in  an  effort  to  satisfy  its 
hunger.  It  has  been  found  that  on  certain  ranges  many  plants  are 
eaten  which  on  other  ranges  are  but  seldom  touched  by  the  same  class 
of  live  stock.  Further,  it  has  been  observed  that  an  animal  in  good 
flesh  will  not,  when  hungry,  eat  offensive  plants  as  readily  as  poor 


26 


hungry  animals  will.  Further,  poor  half -starved  animals  are  more 
easily  and  readily  poisoned  than  when  well  fed.  Thus  the  condition 
of  the  animal  determines  in  a  large  measure  the  extent  to  which  it  will 
graze  poisonous  plants  and  the  probability  of  serious  or  fatal  poisoning. 

THE    SHOWY-LEAVED   MILKWEED    AND    OTHERS   AS 
POISONOUS    PLANTS 

After  two  years  of  observation  in  the  field  and  in  the  feeding  corrals 
we  have  good  reason  to  believe  that  the  narrow-leaved  milkweed  is  of 
far  greater  importance  as  a  poisonous  plant  than  any  other  species  of 
milkweed  growing  in  Nevada.  For  that  reason  only  a  few  experiments 
with  the  other  milkweeds  have  been  made  at  this  Station.  The  follow- 
ing discussion  of  the  other  species  found  in  Nevada  will  give  a  general 
idea  of  their  appearance  and  poisonous  properties : 

The  Showy  Milkweed  (Asclepias  speciosa). 

This  species  of  milkweed  can  be  found  in  many  parts  of  Nevada,  but 
it  does  not  seem  to  be  very  abundant  anywhere.  It  requires  about  the 
same  conditions  for  growth  as  does  the  narrow-leaved  milkweed,  and 
they  are  often  found  growing  together. 

Live  stock  do  not  like  it,  and  it  is  eaten  only  under  stress  of  hunger. 
Often  fields  grazed  by  cattle  may' be  closely  cropped,  with  this  milk- 
weed standing  untouched. 

As  a  poisonous  plant  it  seems  to  be  much  less  important  than,  the 
narrow-leaved  milkweed.  Figure  4  shows  the  general  appearance  of 
this  plant  growing  in  the  field. 

Feeding  experiments  were  made  with  (1)  the  green  leaves,  (2)  the 
leaves  as  they  had  dried  up  naturally  in  the  field,  (3)  the  seeds,  and 
(4)  the  pods. 

TABLE  X 

The  Showy-Leaved  Milkweed— Green  Leaves,   Pods,   Seeds,   and  Dried  Leaves 

Fed  to  Sheep 


> 

«a 

Pg 

3 

cr^ 
ft* 

•    cr 
•  ** 

Date  fed 

Time  fed 

Amount 
fed.lbs. 

Time  symptoms 
observed 

Time  of  death 
or  recovery 

Final 
result 

Part  of  plant 
fed 

4? 

106 

9-10 

10:00  a.  m. 

1 

Negative 

Green  leaves 

84 

103 

9-11 

9:00  a.  m. 

H 

Negative.. 

Green  leaves 

fi4 

99 

9-12 

10:00  a.  m. 

2 

Negative 

Green  leaves 

100 

102 

9-14 

2:00  p.  m. 

2 

Negative 

Green  leaves 

24. 
33 

85 

94 

9-  6 
9-  6 

2:30  p.  m. 
11:30  a.  m. 

9-7—8:00  a.  m. 
9-6  —  6:00  p.  m 

9-10—8:00  a.  m. 
7-  7—8-00  a.  m. 

Recovery.. 
Death 

..  Green  leaves 
Pods 

?,7 

81 

9-12 

'4:00  p.m. 

9-7—7:00  p.  m. 

Before  10:00  p.  m. 

Death  

Seeds 

46 

80 

12-16 

11:30  a.  m. 

| 

Negative 

)  Leaves  dried 

46 

.     80 

12-28 

10:00  a.  m. 

j 

(  in    the    field 

The  above  feedings  seem  to  show  that  ( 1 )  the  green  leaves  are  poison- 
ous, (2)  relatively  large  amounts  are  required  to  cause  poisonous  symp- 
toms in  a  mature  range  ewe,  (3)  the  pods  alone  are  poisonous,  (4)  the 
seeds  are  highly  poisonous,  and  (5)  the  plant  dried  naturally  in  the 
field  contains  little  of  its  original  poisonous  matter. 

Lambs  have  been  fatally  poisoned  by  grazing  upon  the  tender  growth 


27  

of  this  plant  in  the  early  spring  months  when  all  feed  was  scarce,  but 
the  recorded  losses  have  not  been  large. 

Symptoms  of  Poisoning  by  the  Showy  Milkweed. 

The  symptoms  of  poisoning  were  quite  different  from  those  produced 
by  the  narrow-leaved  milkweed.  The  first  symptom  noted  was  extreme 
dullness,  with  a  total  loss  of  appetite  and  a  tendency  to  lie  down.  In 
the  severe  cases  the  breathing  was  distinctly  irregular,  the  breath  being 
expelled  with  a  grunt.  Spasms  were  entirely  absent  and  in  the 
whole  series  symptoms  seemed  much  unlike  those  produced  by  the 
narrow-leaved  milkweed. 

Typical  Cases 

Case  No.  1 — On  September  6,  1918,  at  2  p.  m.  a  yearling  range  lamb 
weighing  85  pounds  was  fed  2£  pounds  of  the  fresh  green  leaves.  At 
8  a.  m.  the  next  day  it  showed  symptoms  of  poisoning.  During  the  day 
of  September  9  it  was  still  sick.  September  10  it  appeared  to  have 
recovered. 

Case  No.  2 — September  6,  1918,  at  11 :  30  a.  m.  a  ewe  weighing  94 
pounds  was  fed  2J  pounds  of  green  pods.  She  was  sick  by  6  p.  m.  the 
same  day.  At  9 :  30  she  was  down ;  the  breathing  was  labored  and 
grunting.  No  other  .symptoms  were,  exhibited.  The  next  morning  at 
8  a.  m.  she  was  found  dead. 

Case  No.  3 — September  12,  1918,  at  4  p.  m.  a  yearling  lamb  weighing 
81  pounds  was  fed  one-half  pound  of  seeds.  At  7  p.  m.  of  the  same 
day  it  was  extremely  dull,  respiration  irregular.  At  8 :  30  p.  m.  it  was 
much  worse ;  the  breathing  was  more  labored  and  each  breath  was 
made  with  a  peculiar  grunt.  At  10  p.  m.  the  animal  was  dead. 

Heart-Leaved  Milkweed  (Asclepias  cordifolia). 

This  plant  is  not  abundantly  distributed  in  the  fields  or  ranges  of 
Nevada.  It  occurs  only  in  the  mountain  valleys,  and  does  not  appear 
to  be  poisonous. 

Five  feedings  of  this  milkweed  were  made  to  sheep,  the  amounts  fed 
ranging  from  one-half  pound  to  2|  pounds.  None  of  the  feedings  so 
far  as  could  be  observed  had  any  poisonous  effect  upon  the  animal. 

This  milkweed  can  be  distinguished  from  the-  showy  milkweed  by 
its  surface  being  smooth  or  free  from  hairs,  while  the  showy  milkweed 
is  covered  with  fine  hairs.  The  base  of  the  leaf  is  heart-shaped,  which 
is  not  the  case  with  the  showy  milkweed.  There  is  little  danger  of  con- 
fusing it  with  the  narrow-leaved  milkweed. 

Prostrate  Milkweed  (Asclepias  cryptoceras). 

This  species  of  milkweed  is  not  important  as  a  poisonous  plant.  It 
grows  sparingly  and  is  not  widely  distributed.  It  is  a  plant  with 
somewhat  tough  leathery  leaves,  and  its  growth  habit  tends  to  be  close 
to  the  ground.  It  may  be  disregarded  as  a  poisonous  plant  of  any 
importance  in  Nevada.  One  feeding  of  3  pounds  at  one  time  was  made 
to  a  mature  sheep  which  did  not  seem  to  be  at  all  injured  by  this  large 
amount. 


SECTION    II 
Technical  Information  Concerning  the  Narrow-Leaved  Milkweed 


Tliis  section  is  not  intended  for  use  by  farmers  and  stockmen : 
The  facts  included  are  for  the  information  of  chemists  and  veteri- 


SYMPTOMS 

The  appearance  of  symptoms  of  poisoning  in  sheep  by  Asclepias 
Mexicana  occurred  about  five  to  seven  hours  after  artificial  or  natural 
feeding  of  the  leaves  or  whole  plant. 

Five  ounces  of  the  dried  plant  appeared  to  be  the  minimum  quantity 
producing  symptoms  of  poisoning  in  sheep.  Three  pounds  of  the  dried 
leaves  appeared  to  be  the  minimum  quantity  producing  toxic  symptoms 
in  a  250-pound  calf,  with  subsequent  recovery. 

The  first  noticeable  symptoms  in  either  cattle  or  sheep  are  general 
depression,  refusal  to  eat,  and  unsteady  wobbly  gait.  The  unsteady 
gait  is  due  to  partial  paralysis  of  the  hind  limbs.  Occasionally  the 
paralysis  is  confined  to  only  one  limb.  This  causes  an  incoordination 
in  movement,  and  the  animal  sways  from  side  to  side.  Marked  muscu- 
lar trembling  is  sometimes  observed,  and  in  a  few  hours  the  animal  lies 
down,  refusing  to  arise.  During  the  period  of  recumbency  tetanic 
spasms  (rigid  extension)  of  the  limbs  occur  at  intervals  of  two  or  three 
minutes. 

There  is  no  perceptible  elevation  of  temperature.  The  pulse  rate 
increases  with  the  duration  of  the  attack  and  shortly  before  death 
may  attain  the  rate  of  180  per  minute,  becoming  very  thready.  Breath- 
ing is  labored  and  rapid.  The  head  is  extended  backward  and  quite 
rigid.  The  attack  may  persist  for  twenty-four  hours,  and  immediately 
before  death  the  animal  lies  in  a  semicomatose  state.  In  case  affected 
animals  recover,  the  gait  is  unsteady  for  two  or  three  days.  In  some 
cases  incoordinate  movements  of  the  hind  limbs  persist  as  long  as  one 
week  after  the  other  symptoms  have  disappeared. 

POST-MORTEM  LESIONS 

These  are  not  especially  characteristic.    . 

Summarizing  the  observations  of  post-mortem  lesions  in  sheep  and 
cattle,  the  following  pathological  changes  were  fairly  constant  in  deaths 
due  to  ingestion  of  Asclepias  Mexicana  : 

The  liver  exhibited  passive  congestion  and  low-grade  cloudy  swelling. 
Kidneys  light  in  color  with  low-grade  cloudy  swelling.  The  mucosa  of 
the  abomasum  may  exhibit  congestion  of  a  moderate  degree  which  may 
be  continuous  throughout  the  small  intestine.  Occasionally  marked 
arborization  of  the  blood-vessels  of  small  intestines  is  observed. 

Occasional  subepicardial  petechial  hemorrhages  are  observed  along 
the  coronary  vessels  and  auriculo-ventricular  border.  The  heart  muscle 
is  pale  and  friable. 

The  pia  mater  in  cerebral  and  cerebellar  regions  exhibited  a  marked 
congestion  on  cut  surfaces;  minute  capillary  hemorrhages  were 
observed  in  the  medullary  portion  of  the  cerebrum  and  cerebellum,  also 
in  the  cropus  striatum.  The  lateral  ventricles  contained  a  moderate 
amount  of  sero-sanguinous  fluid. 

Histopathological  examination  of  selected  tissues  confirmed  the 
observations  made  at  the  autopsy.  In  the  brain  the  hemorrhages  were 
largely  from  the  minute  capillary  vessels.  Occasional  interstitial  capil- 
lary hemorrhages  were  observed  in  the  reticular-  tissue  between  the 
convolutions  of  the  cerebrum. 


31  

The  liver  exhibited  acute  parenchymatous  hepatitis  with  passive  con- 
gestion. The  kidneys  exhibited  low-grade  parenchymatous  nephritis. 
Myocardium,  acute  myositis. 

THE  ACTIVE  PRINCIPLE  OF  ASCLEPIAS  MEXICANA 

Several  species  of  Asclepias  which  are  physiologically  active  have 
been  examined  chemically,  and,  from  the  work  done  by  various  experi- 
menters on  those  investigated,  the  compounds  to  which  the  physiologi- 
cal activity  of  the  plant  may  be  ascribed  apparently  varies  considerably. 
Glucosides  have  been  found  in  several  species,  which  act  on  the  animal 
organism  as  an  emetic.  In  another  species  (syriaca)  a  crystalline 
resinous  substance  was  found  which  acted  as  an  anodyne  and  cathartic. 
Quackenbush  reports  finding  a  crystalline  glucoside  in  Asclepias  tuber- 
om  and  Asclepias  cornuti.  March,  Clawson,  Couch,  and  Eggleston 
(U.  S.  D.  A.,  Bui.  800)  have  recently  reported  preliminary  experiments 
on  Asclepias  yalioides,  a  species  closely  related  to  A.  Mexicana,  in  which 
they  found  evidence  of  the  presence  of  toxic  compounds  having  nar- 
cotic properties  and  also  those  producing  a  spasmodic  type  of  intoxica- 
tion. The  active  principles  were  not  isolated,  but  experiments  on  small 
animals  indicated  the  presence  of  toxic  material  in  successive  extracts 
of  the  dry  plant,  and  gave  some  idea  of  the  solubility  relations  of  these 
materials.  They  found  that  petroleum  ether  removed  no  active  mate- 
rial, but  that  benzol  extracted  substances  which  were  toxic  and  pro- 
duced effects  in  test  animals  similar  to  those  observed  in  poisoning  of 
slieep  by  the  plant.  Ether  and  chloroform  extracts  from  the  material 
already  treated  with  benzol  and  petroleum  ether  also  were  toxic,  indi- 
cating the  possible  presence  of  more  than  one  activ'e  principle.  Other 
solvents  failed  to  remove  toxic  matter  from  the  residue.  Evidence  of 
the  presence  of  a  minute  quantity  of  alkaloids  was  obtained ;  volatile 
poisons  and  saponins  were  not  found.  Alcohol  alone  was  found  to 
extract  all  of  the  toxic  material,  a  part  of  which  was  soluble  in  water 
producing  narcosis,  and  the  part  insoluble  in  water  producing  poisoning 
with  symptoms  typical  of  range  poisoning. 

A  portion  of  the  material  used  in  our  feeding  experiments  was 
examined,  and  results  were  obtained  which  were  in  some  ways  similar 
to  those  reported  on  Asclepias  galioides. 

A  small  quantity  of  the  plant  was  extracted  successively  with  sol- 
vents and  the  amounts  extracted  by  each  were  as  follows : 

Benzol 10.55% 

Ether  0.64% 

Chloroform  0.70% 

Ethyl  acetate 2.68% 

Alcohol 0.46% 

Each  of  the  residues  from  these  extractions  were  administered  to 
guinea  pigs  by  mouth  in  amounts  corresponding  in  each  case  to  five 
grams  of  the  dry  plant,  and  all  appeared  to  be  nontoxic,  except  the 
benzol  extract.  Thus  benzol  is  capable  of  removing  all  of  the  toxic 
substances.  No  reactions  were  noted  in  the  cases  of  the  materials 
extracted  by  the  other  solvents,  the  animals  appearing  normal. 

Another  small  portion  of  the  dry  powder  was  studied  by  extracting 
with  dilute  acid  and  testing  with  the  general  alkaloidal  reagents.  With 
each  reagent  used,  indication  was  obtained  of  the  presence  of  alka- 


-82- 

loids.    No  alkaloidal  preparations  were  made  for  animal  experiments! 
A  larger  portion  of  the  plant  which  had  been  dried  was  extracte 
with  alcohol  by  percolation.     The  alcohol  was  then  removed,  and  th« 
remaining  sirup  was  evaporated  to  dryness  and  extracted  repeatedljj 
with  boiling  water.    The  aqueous  extract  so  obtained  was  clear  and  oJ 
a  dark-brown  color.     It  had  a  very  sweet  taste  with  a  slightly  bittei 
after-taste.     The  residue  from  this  extraction  was  a  black  resinoi 
mass. 

The  aqueous  extract  and  black  residue  were  administered  to  a  guim 
pig  by  mouth.  The  amounts  given  corresponded  to  5  grams  of  th< 
dried  plant  in  each  case.  The  aqueous  extract  proved  to  be  nontoxi( 
the  animal  remaining  normal,  but  the  black  residue  was  fatal  in  thre^ 
hours.  The  symptoms  exhibited  by  this  animal  were  the  same  as  the 
shown  by  the  one  to  which  was  given  the  benzol  extract.  Apparently 
then,  the  active  material  of  Asclepias  Mexicana  differs  from  that  foum 
in  Asclepias  galioides  by  Marsh,  Clawson,  Couch,  and  Eggleston  h 
that  the  substance  producing  narcosis  found  by  them  in  Asclepia\ 
galioides  is  lacking  in  this  plant.  It  is  possible,  however,  that  witl 
doses  representing  larger  quantities  of  the  plant  the  narcotic  effec] 
might  be  present  and  more  noticeable. 


Makers 

Syracuse,  N.  Y. 

PAT.  JAN.  21 ,1908 


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